The disclosure relates generally to display systems and related methods that utilize more than three pixel component values per pixel, such as but not limited to, display systems (including video display systems or printers) that use an RGBW format, RGBA format or other pixel format that requires communication of more than three pixel component values per pixel.
Display systems are known to use color formats that employ more than three data values per pixel, such as RGBW. Each pixel requires the storage of 4 component values in frame buffer memory. The system communicates these pixel values across buses from frame buffers to display controllers or across video interfaces such as a Display Port type interface, digital video interface (DVI) or other suitable interface, to one or more displays.
One known method of communicating the four pixel component values to a display is to use multiple video data interfaces in parallel. For example one interface can carry color data, while the other carries the alpha data. This is commonly used in video production studios, where two HD-SDI interface cables are used in parallel to carry color and alpha data for the same video data stream.
Another known system is to alternate the sending of different data components in sequential pixel cycles. For example even pixel cycles may carry RGB color data, and odd pixel cycles may carry alpha data. The interleave could be on single pixels, groups of pixels, lines or frames.
Yet another approach is to “pack” data values so that each “pixel” cycle of the video interface carries only three components from single image pixel, or parts of two different image pixels. For example sending RGBW data over a 3 value/cycle interface could be done as:
Cycle#R valueG valueB value0R0G0B01W0R1G12B1W1R23G2B2W24R3G3B3And so on.
It can be seen that 3 RGBW pixel values may be packed into every 4 data cycles on the video data interface. Similar packings can be done for 4, 5 or more components per image pixel. However such packing may unnecessarily limit the performance of a display system.
It is also known to convert from a three color space to a four color space, for example, using gamut remapping as known in the art. For example, display systems may employ, for example, graphics processors and a plurality of corresponding display controllers. The display controller obtains stored pixel component values from one or more frame buffers. A single gamut remap engine in one of the graphics processors, for example, may perform the conversion process to go from a three component value format to a four or more pixel component value format. A display controller may also include the remap engine. In some systems, multiple display controllers wherein one display controller uses gamut remapping to generate RGB component data and another display controller uses gamut remapping to generate corresponding alpha data. The resulting RGB component data is output on one cable to a composite board and the corresponding alpha data is output on a separate cable to the composite board. The composite board composites the RGB and alpha data for output on one or more displays.
The DisplayPort 1.2 standard is a digital interface to connect with monitors (displays). The DisplayPort 1.2 standard enables packet based multi-streaming of different video streams for multiple monitors so that a hub or computer may provide differing display streams to differing monitors. As such, a single cable or wireless interface may be employed.
DisplayPort 1.2 enables multiple independent display streams for different monitors, that are interleaved. As such, a few pixels for each monitor may be interleaved in packets that may be generated by an encoder. Also, one display may be a branch device or hub that receives streams for multiple displays (e.g., sink/logical branch), such a sink typically processes one or more streams, each stream dedicated to a single image and passes through the rest of the streams to other sinks/devices. There is identification data to identify subcomponents of a packet so that bytes from a packet may be identified to correspond to the same stream and hence the same monitor. One packet can include pixels for multiple displays. One display (e.g., video sink device) may also be set up as a logical branch device that receives multiple streams and displays multiple streams as separate streaming video streams, each having different images. A unique address is assigned to each logical sink in the logical branch device and a common global universal ID (GUID) is used for the logical sinks.
It has been proposed, for example, for a monochrome display using a DisplayPort 1.2 interface to use a single data value per pixel pack mode for display port video streams for use with monochrome displays. As such, DisplayPort 1.2 includes a mechanism to operate in a Y only packing mode. One data value for each pixel is utilized for monochrome monitors. This Y only packing mode uses one standalone stream to provide the Y data for a monochrome monitor. The DisplayPort 1.2 interface standard only contemplates sending a single stream for each image to a device, although a device may receive multiple streams each for a different image to facilitate picture in picture type display. For example, a single image stream may contain either a single component, such as Y only for a monochrome display, or three components such as an RGB based stream for a single image stream.
It would be desirable to provide an improved display system that better accommodated pixel data formats that used more than three pixel component data values per pixel.